#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>

#define MAX_DATA 512
#define MAX_ROWS 100

struct Address {
	int id;
	int set;
	char name[MAX_DATA];
	char email[MAX_DATA];
};

struct Database {
	struct Address rows[MAX_ROWS];
};

struct Connection {
	FILE *file;
	struct Database *db;
};

void die(const char *message){
	if(errno){
		perror(message);
	}else{
		printf("ERROR: %s\n",message);
	}
	exit(1);
}

void Address_print(struct Address *addr){
	printf("%d %s %s\n",
			addr->id, addr->name, addr->email);
}

void Database_load(struct Connection *conn){
	int rc = fread(conn->db, sizeof(struct Database), 1, conn->file);
	if(rc != 1) die("Failed to load database.");
}

struct Connection *Database_open(const char *filename, char mode){
	struct Connection *conn = (struct Connection *)malloc(sizeof(struct Connection));
	if(!conn) die("Memory error.");

	conn->db = (struct Database *)malloc(sizeof(struct Database));
	if(!conn->db) die("Memory error.");

	if(mode == 'c'){
		conn->file = fopen(filename, "w");
	}else{
		conn->file = fopen(filename, "r+");
		if (conn->file){
			Database_load(conn);
		}
	}

	if(!conn->file) die("Failed to open the file.");

	return conn;
}

void Database_close(struct Connection *conn){
	if(conn){
		if(conn->file) fclose(conn->file);
		if(conn->db) free(conn->db);
		free(conn);
	}
}

void Database_write(struct Connection *conn){
	rewind(conn->file);

	int rc = fwrite(conn->db, sizeof(struct Database), 1, conn->file);
	if(rc != 1) die("Failed to write database.");

	rc = fflush(conn->file);
	if(rc == -1) die("Cannot flush database.");
}

void Database_create(struct Connection *conn){
	int i = 0;
	for(i=0; i< MAX_ROWS; i++){
		//make a prototype to initialize it
		struct Address addr={.id = i, .set = 0};
		//then just assign it
		conn->db->rows[i] = addr;
	}
}

void Database_set(struct Connection *conn, int id, const char *name, const char *email){
	struct Address *addr = &conn->db->rows[id];
	if(addr->set) die("Already, delete it first.");

	addr->set = 1;
	// WARNING: bug, read the "How To Break It" and fix this
	char *res = strncpy(addr->name, name, MAX_DATA);
	//demonstrate the strncpy bug
	if(!res) die("Name copy failed.");

	res = strncpy(addr->email, email,MAX_DATA);
	if(!res) die("Email copy failed.");
}


void Database_get(struct Connection *conn, int id){
	struct Address *addr = &conn->db->rows[id];

	if(addr->set){
		Address_print(addr);
	}else{
		die("ID is not set.");
	}
}

void Database_delete(struct Connection *conn, int id){
	struct Address addr = {.id = id, .set=0};
	conn->db->rows[id] = addr;
}

void Database_list(struct Connection *conn){
	int i = 0;
	struct Database *db = conn->db;

	for(i=0; i<MAX_ROWS; i++){
		struct Address *cur = &db->rows[i];

		if(cur->set){
			Address_print(cur);
		}
	}
}



int main(int argc, char *argv[])
{
 	if(argc < 3) die("USAGE: ex17 <dbfile> <action> [action params].");

 	char *filename = argv[1];
 	char action = argv[2][0];
 	struct Connection *conn = Database_open(filename, action);

 	int id = 0;

 	if(argc > 3) id = atoi(argv[3]);
 	if(id >= MAX_ROWS) die("There's not that many record.");

 	switch(action){
 		case 'c':
 			Database_create(conn);
 			Database_write(conn);
 			break;
 		case 'g':
 			if(argc !=4) die("Need an id to get");
 			Database_get(conn, id);
 			break;
 		case 's':
 			if(argc != 6) die("Need id, name, email to set.");

 			Database_set(conn, id, argv[4], argv[5]);
 			Database_write(conn);
 			break;
 		case 'd':
 			if(argc != 4) die("Need id to delete.");

 			Database_delete(conn, id);
 			Database_write(conn);
 			break;
 		case 'l':
 			Database_list(conn);
 			break;
 		default:
 			die("Invalid action, only: c=create, g=get, s=set, d=delete, l=list.");

 	}

 	Database_close(conn);

 	return 0;
}